Optical materials such as conventional optical glass all have a relative permeability that is approximately 1 and have a relative permittivity that is greater than 1, and thus have refractive index with a positive value greater than 1. In view of this situation, researches are made with respect to so-called meta-materials that are substances provided with a structure smaller than the wavelength of a light as an objective to which the meta-materials are to be applied and greater than an atom or molecule and exhibiting a relative permeability value and/or relative permittivity value which are/is unobtainable with a substance in the natural world. Further, with respect for example to a microwave having a wavelength of 6 cm (frequency: 5 GHz), a large number of small split-ring resonators having a negative relative permeability and a large number of thin metallic lines having a negative relative permittivity and arranged in parallel are combined and thus a substance (structure) having a negative refractive index is realized (see, for example, Non-patent Literature 1).
In the recent years, in order to realize a substance having a negative refractive index to lights in the infrared to visible regions, for example, such a substance is theoretically proposed having a plurality of minute split-ring resonators and a relative permeability that is greatly different from 1 (including a negative value) with respect to a light of which wavelength is about 1,000 nm to about 400 nm (see, for example, Non-patent Literature 2). By combining the minute split-ring resonators (having the relative permeability in a negative range) and another substance having a negative relative permittivity, it is possible to realize the substance having the negative refractive index to the lights in the infrared to visible regions.